This invention relates to crash protection devices for use in vehicles, and particularly to crash protection devices of the type in which a bag is inflated automatically under severe crash conditions to act as a cushion to restrict and cushion forward motion of an occupant of a vehicle with respect to the vehicle.
It is known to incorporate inflatable bag crash protection devices into vehicle steering wheels and also into the fascia panel of the vehicle in front of the front seat passenger. In known devices, the bag is contained within a housing forming part of the steering wheel of a vehicle. The housing includes a front cover whose exterior surface is designed to blend in with the rest of the interior of the vehicle On impact, the bag is inflated and forces its way out of the housing by tearing the front cover along one or more predetermined tear lines formed in the cover. These tear lines are defined by grooves or weakened zones moulded into the internal surface of the front cover to reduce the thickness thereof.
In order for the front cover to blend in with the interior of the vehicle, it is desirable to construct the front cover out of a material which complements the rest of the vehicle interior. It is not easy to form tear lines in some materials and so the range of materials available for use is restricted.
Commonly, the provision of grooves in the interior surface of the front cover can be discerned externally as apparent blemishes. It is therefore necessary to include features on the outer surface of the front cover to disguise such apparent blemishes. In order to make the front cover blend in with the rest of the interior of the vehicle, these features may not be desirable. The tear lines are also weak points on the front cover and so render the front cover more prone to accidental damage.
GB-A-2228235 (and corresponding DE-A-3942694) and GB-A-2241665 disclose crash protection devices of the type where the inflatable bag is contained within a housing having a front cover. Such front cover has a relatively hard core and a relatively soft external surface layer in situ moulded over the core, and the weakened zones are formed in the relatively hard core. Whilst such an arrangement does permit a certain degree of flexibility of design to enable the front cover to blend in with the interior of the vehicle, the external surface layer is required to have properties which do not interfere with correct breaking of the core upon inflation of the bag. Thus, for example, the use of fabric or leather to match the interior of the vehicle will normally be precluded in devices of this type.
In vehicles including crash protection devices as described above, it is difficult to include switches for controlling other devices included in the vehicle, for example, the horn, on the steering wheel because the whole device needs to be able to move when the switch is activated. It is also difficult to fix decorated emblems or other embellishments on the front cover as they may become disconnected from the front cover on inflation of the bag, and be a hazard to the vehicle occupants.